1. Technical Field
The present invention relates to a mounting method and mounting device for a light emitting element, for use at the time of mounting a light emitting element such as a laser chip or LED on a board or the like.
2. Background Art
In general, in order to carry out bonding of electronic parts to a board with high precision, an arrangement is usually made wherein an alignment mark is provided on the electronic parts beforehand, this alignment mark and a mark on the board are subjected to alignment, and then bonding of the electronic parts to the board is carried out. However, providing an alignment mark on parts leads to a problem wherein the accuracy of positioning on a board is also affected by the margin of error in providing an alignment mark, as well as an increase in cost.
For an electronic light emitting element such as a laser chip or LED, it is desirable to carry out bonding onto a board based on the optic axis along which the light emitting element emits light.
FIG. 18 illustrates an example in which an edge-emitting-type laser chip 100 is bonded to a waveguide board 101. A waveguide 102 for letting light pass is horizontally formed in the waveguide board 101, alignment is performed such that this waveguide 102 is on the optic axis of the laser chip 100, and bonding is performed through an electroconductive connecting material 103. To the portion on the side opposite to the portion of the waveguide board 101 to which the laser chip 100 is bonded across the waveguide 102, an optical fiber 104 is attached so as to align its axial center with the axial center of the waveguide 102. Thus, the light generated by the laser chip 100 is transmitted to an optical communications line through the optical fiber 104.
When bonding the laser chip 100 to the waveguide board 101 as described above, alignment should be precisely performed such that the waveguide 102 and the optic axis of the laser chip 100 are on the same axis. To this end, the optic axis of the laser chip 100 needs to be aligned with the waveguide 102 in the X-axis, Y-axis (optic-axis direction), Z-axis, and θ-axis (compare FIG. 14) directions. In particular, accuracy of positioning on the order of a micron in the X-axis direction and in the Z-axis direction is necessary.
Patent Document 1: Japanese Examined Patent Application Publication No. 7-46747.
In Patent Document 1, a method has been proposed wherein an intermediate chip is disposed on a post on the basis of a positioning plate, a laser chip is disposed on this intermediate chip, the laser chip is made to emit light, correction of rotational direction is performed based on the light emission direction thereof, following which bonding of the three articles of the post, intermediate chip, and laser chip is simultaneously carried out. However, this method includes making the laser chip emit light, recognizing the direction thereof, and performing rotation correction on that occasion, so only rough adjustment can be performed with this method, and attempting to adjust the orientation with high precision requires time. Also, the relative spatial relationships between the laser chip and the post are not recognized, so that in the event of mounting a laser chip on a waveguide board, high accuracy of position cannot be expected even with this method.
Patent Document 2: Japanese Examined Patent Application Publication No. 7-105575
In Patent Document 2, a method has been proposed wherein a laser chip is disposed on an intermediate stage, the laser chip is made to emit light, the X, Y, and θ axes of the optic axis thereof are measured, the light emission direction is corrected depending on the measurement, following which the laser chip is subjected to bonding to the post or the like. In this case, the light emission direction of the laser chip can be recognized with precision, but the relative spatial relationships as to the post serving as an object to be bonded cannot be recognized, so the position and attitude of a mounting state cannot necessarily be secured. In particular, bonding is frequently accompanied with not only pressure but also heating, and consequently, attitude error is caused due to heat deformation or the like at the time of heat bonding, and therefore accuracy of position in the mounting state is not high.
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2000-150970
Patent Document 3 describes a method for performing image recognition of the outer diameter datum point coordinates of and the luminescence center of a light emitting element, and an element. See FIGS. 9 and 10. This method relates to a method for mounting two or more light emitting elements having an upward optic axis on a board such that the luminescence center thereof becomes equal intervals, and the spatial relationships between the two or more light emitting elements can be set precisely, but the board has nothing used as a datum reference, and accordingly, the relative positions in a mounting state between the light emitting elements and the board cannot be secured. Accordingly, even if this method is applied to mounting a laser chip on a waveguide board, high accuracy of position between the waveguide board and the laser chip cannot be obtained.